1. Field of the Invention
The present invention relates to an improved method for preparing fat-and-oil-coated sweetener compositions, for improving heat stability, and the compositions so prepared.
2. Discussion of the Background
For improving the heat stability of peptide type sweeteners, such as aspartame, etc., in which heat stability comes into question, the following methods have been attempted or are known.
(1) A sweetener (such as, e.g., aspartame) is mixed with heated and melted oils and fats, and the mixture is cooled to solidify as is or after spreading to obtain a flat plate. The solid is then ground into a powder.
(2) A powdery sweetener is granulated into dens spherical particles using a special device, and the surface is then coated with heated and melted oils and fats (Japanese Patent Application Kokai No. 2-500165).
(3) A method for spray cooling in which a sweetener (such as, e.g. aspartame) is mixed with heated and melted oils and fats, and the mixture is cooled to solidify by spraying into the air to obtain spherical particles.
However, the methods described above suffer from the following problems, respectively.
(1) According to the first method, the particles are obtained by mechanical grinding, so that no spherical particles are obtained. The particles have a large surface area, and their shape is also complicated and hence, any good coating effect with oils and fats cannot be expected. When aspartame is mixed in a high concentration, the viscosity markedly increases or gelation occurs so that handling becomes difficult.
(2) According to the second method, the coating effect is good but a graining step with a special device is required as a pretreatment so that the method is costly.
(3) The third method fails to increase the concentration of aspartame as will be later described. As a result, it is required to increase the amount of the oils and fats-coated particles incorporated into the food, resulting in an economical disadvantage. Furthermore, since the amount of oils and fats used becomes large, such might adversely affect the food to which the composition is added.
That is, in view of the coating effect, it is most advantageous that the oils-and-fats-coated particles have a spherical shape. As the method, there is generally known Method (3) in which cooling to solidify by spraying the mixture into the air (spray cooling method). In this case, the smaller the particle diameter of the core material, the higher the coating effect. In the case of a nucleic acid, etc., the particle diameter of a nucleic acid as the core material is reduced to 5% or smaller based on the particle diameter of a coating material (Japanese Patent Application Kokai No. 61-238335), whereby a high coating effect and an effect of reducing the rate of eluting into water are achieved. In the case that the coating property of aspartame is improved by this method, however, aspartame having a small particle diameter causes gelation of melted oils and fats or causes a marked increase of the viscosity, even in a low concentration (in the case of aspartame having an average particle diameter of 10 micron or less, the viscosity increase is remarkable even in a concentration of about 5% by weight). Such a viscosity increase becomes a serious obstacle in spraying.
Thus, there remains a need for a method of preventing the increase in viscosity or gelation which is a problem inherently involved in using aspartame or the like as the core material, so that good fluidity is maintained to make spraying possible, thereby to obtain spherical particles having an excellent coating effect.